but the other two lines are real properties. Shouldn't they be
annotate-{page,headers} , to keep in style with the other
\paper{variable-with-hyphens} stuff?

Yes. Please change.

Sorry, I was unclear. I've changed annotate-spacing in the example,
but annotatepage and annotateheaders are lilypond properties without
hyphens. If changing them is as simple of doing "sed
/s/annotatepage/annotate-page/ * -r" I could do it, but I'm not
comfortable doing anything else to the lilypond source code.